Abstract
The rotation speed of a mill is an important factor related to its operation and grinding efficiency. Analysis and regulation of the optimal speed under different working conditions can effectively reduce energy loss, improve productivity, and extend the service life of the equipment. However, the relationship between the optimal speed and different operating parameters has not received much attention. In this study, the relationship between the optimal speed and particle size and number was investigated using discrete element method (DEM). An improved exponential approaching law sliding mode control method is proposed to track the optimal speed of the mill. Firstly, a simulation was carried out to investigate the relationship between the optimal speed and different operating parameters under cross-over testing. The model of the relationships between the optimal rotation speed and the size and number of particles was established based on the response surface method. An improved sliding mode control using exponential approaching law is proposed to track the optimal speed, and simulation results show it can improve the stability and speed of sliding mode control near the sliding surface.
Highlights
In modern mineral processing, semi-autogenous (SAG) mills are important grinding equipment.A SAG mill has the advantages of high operation rate, large output, and large crushing ratio, which makes SAG mills have the characteristics of short process time, low management cost, and suitability for large-scale production compared to other mills
In each each run divided into several small areas according to the and run of of simulation, simulation,the thedropping droppingarea areawas was divided into several small areas according to abscissa, the abscissa, the of particles dropped in each in small wasarea calculated to analyzetothe dropping andnumber the number of particles dropped eacharea small was calculated analyze themovement dropping of particles in the drum
In order to improve the stability of the system approaching motion, the exponential approaching law is chosen to weaken the chattering of sliding mode control [26]
Summary
Semi-autogenous (SAG) mills are important grinding equipment. Discrete element method (DEM), which can provide dynamic information of individual particles and handle multiple particle contacts [15], has become an important tool for conducting research on large scale equipment in mineral processing [16]. This method has been used extensively to improve the efficiency of the comminution devices [17]. Studying tumbling mills (e.g., ball mills and SAG mills) using DEM has attracted many researchers’ interests as reviewed by Weerasekara et al [23] in the fields of charge motion and power draw, effects of grinding media shape, breakage of particles, and so on.
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